Chelsea defender Cesar Azpilicueta reflected one "one of the worst nights" of his career as the Blues fell to a 6-0 defeat at Manchester City on Sunday.
Sergio Aguero scored a record-equalling hat-trick as Man City powered back to the top of the Premier League with a sensational victory at the Etihad.
The prolific Argentinian joined Alan Shearer on 11 Premier League trebles as the champions returned to their ruthless best in a one-sided encounter.
Most of the damage came in a whirlwind opening 25 minutes, with Aguero hitting his first two of the afternoon between strikes from Raheem Sterling and Ilkay Gundogan.
That established Aguero as City's record league goalscorer, surpassing the 158 goals of Eric Brook and Tommy Johnson, and he later extended his tally to 160 by completing his treble from the penalty spot.
Sterling put the seal on the rout by adding his second 10 minutes from time.
Aguero should even have had more, having missed a sitter in the early stages and headed against bar on a dismal afternoon for Chelsea, whose manager Maurizio Sarri headed straight down the tunnel at full-time.
While City responded in the perfect manner to Liverpool's victory on Saturday, Chelsea looked far from the top-four side they aspire to be. The loss left them outside the Champions League places and the pressure is mounting on manager Sarri.
It was Chelsea's heaviest defeat since losing 7-0 to Nottingham Forest in 1991.
Speaking after the game, Azpilicueta - who conceded the penalty with a foul on Sterling, and apologised to Chelsea fans at full-time - told Sky Sports: "It is one of the worst nights in my career. It is difficult to explain what happened.
"The first five or six minutes went well but that is not enough. It is very frustrating and disappointing. We are conceding a lot of goals and we cannot accept that.
"When you lose 6-0 we have to accept we didn't play well and made errors. We knew it would be tough. When we won at Stamford Bridge it was because we played well and were together. Today was not the case.
"All I can do is apologise to the fans because it is not acceptable."
Additional reporting by the Press Association.
